Amyloid status imputed from a multimodal classifier including structural MRI distinguishes progressors from nonprogressors in a mild Alzheimer's disease clinical trial cohort.

ABSTRACT

INTRODUCTION: Mild-Alzheimer's disease (AD) subjects without significant Aß pathology represent a confounding finding for clinical trials because they may not progress clinically on the expected trajectory, adding variance into analyses where slowing of progression is being measured. METHODS: A prediction model based on structural magnetic resonance imaging (MRI) in combination with baseline demographics and clinical measurements was used to impute Aß status of a placebo-treated mild-AD sub-cohort (N = 385) of patients participating in global phase 3 trials. The clinical trajectories of this cohort were evaluated over 18 months duration of the trial, stratified by imputed Aß status within a mixed-model repeated measures statistical framework. RESULTS: In the imputed Aß-positive cohort, both cognitive (ADAS-Cog14 and MMSE) and functional (ADCS-iADL) measures declined more rapidly than in the undifferentiated population. DISCUSSION: Our results demonstrate imputing Aß status from MRI scans in mild-AD subjects may be a useful screening tool in global clinical trials if amyloid measurement is not available.